Material Removal Rate, Tool Wear Rate and Surface Roughness Analysis of EDM Process

IJSRD - International Journal for Scientific Research & Development| Vol. 1, Issue 3, 2013 | ISSN (online): 2321-0613
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Material Removal Rate, Tool Wear Rate and Surface Roughness Analysis
of EDM Process
Mehul Manoharan1
Abhi P. Valera2
Shrey M. Trivedi 3
Kapil S Banker 4
4
Assistant Professor
1, 2, 3, 4
Department of Mechanical Engineering
1, 2, 3, 4
Shankersinh Vaghela Bapu Institute of Technology, GTU, Ahmedabad, Gujarat – India
Abstract— Electrical discharge machining (EDM) is one of
the non-traditional machining processes, based on thermo
electric energy between the work piece and an electrode. In
this process, the material removal is occurred electro
thermally by a series of successive discrete discharges
between electrode and the work piece. The parametric
analysis of the EDM process by using different electrode
materials has been carried out. The Material Removal Rate
(MRR), Tool Wear Rate (TWR) and Surface Roughness
(SR) is measured and recorded for detailed analysis.
Different electrode
I. INTRODUCTION TO DIE-SINKING EDM
In the Die-Sinker EDM Machining process [1], two
metal parts submerged in an insulating liquid are connected
to a source of current which is switched on and off
automatically depending on the parameters set on the
controller. When the current is switched on, an electric
tension is created between the two metal parts. If the two
parts are brought together to within a minimum gap, the
electrical tension is discharged and a spark jumps across.
Where it strikes, the metal is heated up so much that it
melts. Sinker EDM, also called cavity type EDM or volume
EDM consists of an electrode and work piece submerged in
an materials viz. Aluminium, Copper, Bronze and
workpiece material as Stainless Steel 304 have been
employed for the set of experiments. The dielectric used is
Kerosene diluted with water. The objective of the analysis is
to identify the best material in terms of higher MRR, lower
TWR, and excellent surface finish. The different parameters
considered while carrying out the experiments on the Die-
Sinking EDM would be the voltage and current applied,
depth of cut, time required etc.
EDM, NCM, MRR, TWR, Surface Roughness,
Parametric Analysis insulating liquid such as, oil or, less
frequently, other dielectric fluids. The electrode and
workpiece are connected to a suitable power supply. The
power supply generates an electrical potential between the
two parts. As the electrode approaches the work piece,
dielectric breakdown occurs in the fluid, forming a plasma
channel, and a small spark jumps. These sparks usually
strike one at a time because it is very unlikely that different
locations in the inter-electrode space have the identical local
electrical characteristics which would enable a spark to
occur simultaneously in all such locations. These sparks
happen in huge numbers at seemingly random locations
between the electrode and the work piece. As the base metal
is eroded, and the spark gap subsequently increased, the
electrode is lowered automatically by the machine so that
the process can continue uninterrupted.
Several hundred thousand sparks occur per second, with the
actual duty cycle carefully controlled by the setup
parameters.
Fig: 1 Die-Sinker EDM Setup [1]
II. LITERATURE REVIEW
In this paper few selected research paper related to
Die-sinker EDM with effect of MRR, TWR, surface
roughness (SR) and work piece material have been
discussed.
Nikhil Kumar et al. conducted experiments [1] with
positive polarity of electrode. The pulsed discharge current
was applied in various steps in positive mode. It is capable
of ma chining of hard material component such as heat
treated tool steels, composites, super alloys, ceramics,
carbides, heat resistant steels etc. The higher carbon grades
are typically used for such applications as stamping dies,
metal cutting tools, etc. AISI grades of tool steel is the most
common scale used to identify various grades of tool steel.
In this experiment using AISI P20 tool steel material, that is
a pre hardened high tensile tool steel which offers ready
machine ability in the hardened and tempered condition,
therefore does not require further heat treatment. Subsequent
component modifications can easily be carried out. Graphite
electrode is more favourable than the copper electrode for
the machining of steel work piece for MRR and TWR. It is
also found that overall cost for machining of hard material
with the use of graphite electrode is comparatively less than
copper electrode.
Rajesh Choudhary et al. conducted [2]
investigations on the machining of EN-3 1 die steel with
different electrode materials (copper, brass and graphite)
with electrical discharge machining (EDM) process. This
study presents the analysis and evaluation of heat affected

Material Removal Rate, Tool Wear Rate and Surface Roughness Analysis of EDM Process
(IJSRD/Vol. 1/Issue 3/2013/0001)
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408
zones (HAZ) of the workpiece surfaces machined using
different tool electrodes by EDM. The kerosene oil of
commercial grade has been used as dielectric fluid. From the
micro-structural analysis study it has been observed that
heat affected zone is much deeper in the specimen machined
by graphite electrode as compared to other tool electrodes.
The following conclusions were arrived at: i) For the EN-3 I
work material. Copper electrodes have high MRR as
compared to the machining performed by graphite and brass
electrodes. ii) Among the three tested electrode materials,
brass electrodes produce comparatively high surface finish
for the tested work material at high values of discharge
current, while graphite shows the poor surface finish.
H S Payal et al. performed experiments [3] to
determine parameters effecting surface roughness along
with structural analysis of surfaces with respect to material
removal parameters. Experimental work was conducted on
EN-31 tool steel with copper, brass and graphite as tool
electrodes with kerosene oil as dielectric fluid. Detailed
analysis of structural features of machined surface was done
by using Scanning Electron Microscope (SEM) and optical
microscope to understand the mode of heat affected zone
(HAZ) which alternatively affects structure of machined
workpiece and hence tool life while investigating EDM
surface by micrographs. It was observed that molten mass
has been removed from surface as ligaments and sheets. In
some cases, it is removed as chunks, which being in molten
slate stuck to surface. MRR increases with increase in
discharge current for all three electrodes. However, in case
of brass and graphite, it decreases after some limit, due to
pulse energy increases as the current increases. MRR does
not observe linearity with pulse energy, may be due to the
possible losses of thermal energy by conduction to
surrounding material and dielectric fluid. An increase in
current beyond certain limit for a given electrode area and
material has adverse effect on MRR.
S.H.Tomadi et al. has evaluated the [4]
effectiveness of EDM process with tungsten carbide, WC-
Co in terms of the material removal rate, the relative wear
ratio and the surface finish quality of the workpiece
produced. It is observed that copper tungsten is most
suitable for use as the tool electrode in EDM of WC-Co.
Better machining performance is obtained generally with the
electrode as the cathode and the workpiece as an anode. The
Full Factorial Design of Experiment (DOE) is very useful in
analyzing the optimum condition of parameters, main effect,
and the significance of individual parameter to surface
roughness, material removal rate and electrode wear of
material. In the case of the Ra parameter, the most
influential factors were voltage followed by the pulse off
time, while the peak current and pulse on time was not
significant at the considered confidence level. In order to
obtain a good surface finish in the case of tungsten carbide,
low values should be used for peak current, pulse off time
and voltage. In the case of material removal rate, it was seen
that pulse on time factor was the most influential, followed
by voltage, peak current, and pulse off time.
J. A. Sa´nchez et al. describes [5] about the
development of sinking and wire electro-discharge
machining technology for two ceramics with a promising
future (boron carbide and silicon infiltrated silicon carbide).
The high removal rates, as well as the possibility of
obtaining an excellent surface finish, prove the feasibility of
the industrial application of this production method. I n
t h e c a s e o f W E D M , cutting rates of 21.3
mm3
min-1
for B4C and 114 mm2 min1 for SiSiC were
obtained. In the case of finishing cuts, the best roughness
values were Ra 0.56 µm for B4C and Ra 3.5 µm for
SiSiC. In the case of SEDM, the maximum removal rate is
obtained when a set of capacitors is connected in parallel
between the electrode and the workpiece. Thus, removal
rates of 8.3 mm3
min-1
for B4C and 10.1 mm3
min-1
for SiSiC
were obtained, always using copper electrodes.
Kuldeep Ojha et al. proposed a [6] hybrid
machining process (HMP) involving high-speed machining
(HSM). An increase in material removal rate was reported
but success of such machining was found to be dependent to
a large extent on the availability and performance of a single
cutting / dielectric fluid. Experimental results showed that
material removal rate could be increased greatly by
introducing ultrasonic vibration. The comparison of MRR in
traditional EDM in gas and ultrasonic vibration assisted gas
medium EDM for machining cemented carbides workpiece
was reported. MRR was found considerably higher for a
particular discharge pulse-on time for ultrasonic vibration
assisted machining.
Fig. 2 : Vibratory, rotary and vibro-rotary electrode [6]
Hitesh B. Prajapati et al. has [7] concluded the
following:
 Peak current, pulse off time and pulse on time
significantly affects the MRR and SR in EDM.
 Analysis of variance shows that peak current and
Pulse on time are having more influence to material removal
rate.
 Surface roughness was mainly affected by the
current and pulse on time. At higher value of current causes
the more surface roughness. Higher surface finish can be
achieved value can be achieved at lower current.
 Peak current and pulse on time are the most
influential parameters for reducing surface quality.
 The Brass electrode gives the poor material
removal rate and gives the better than surface finish than
other two electrodes.
 The graphite electrode gives the most material
removal rate and gives the better than surface roughness but
it gives high electrode wear ratio.
 The material powder electrode gives the better
MRR than solid electrode.
 Similarly Brass electrodes gives lowest MRR
among three electrodes when Peak current = 17 A, 45 μs
pulse on time, 60 μs pulse on time.

Material Removal Rate, Tool Wear Rate and Surface Roughness Analysis of EDM Process
(IJSRD/Vol. 1/Issue 3/2013/0001)
All rights reserved by www.ijsrd.com
409
 Brass electrodes gives better surface finishing
among three electrodes when Peak current = 17 A, 65 μs
pulse on time, 45 μs pulse on time.
 Similarly copper electrodes gives poor surface
finishing among three electrodes when Peak current = 28 A,
65 μs pulse on time, 60 μs pulse on time.
Sharanjit Singh et al. has described [8] that the
main factors determining the suitability of material are, we
can achieve maximum MRR, wear ratio, cost and ease with
which it can be shaped or fabricated to the desired shape.
Generally, by using a sufficient number of electrodes of
material having a low wear ratio, it is possible to produce
the same accuracy of machining as with a single electrode of
material with a high ratio. Keeping in mind technical and
economic considerations various materials that can be used
as electrode is shown in table 1
Table.1 : Selection of electrode material [8]
Fig.3 : Classification of major EDM research areas [8]
III. CONCLUSION
For high discharge current, copper electrodes show
highest MRR, whereas Brass gives good surface finish and
normal MRR. Since EDM is a thermal method, special
attention must be paid to surface integrity. Surface and
subsurface damage may be induced owing to thermal fatigue
or to the material recast on the surface after removal. The
MRR could be improved by carrying out research on
electrode design, process parameters, EDM variations,
powder mixed dielectric and electrically insulated
electrodes. It is found that the basis of controlling and
improving MRR mostly relies on empirical methods. This is
largely due to stochastic nature of the sparking phenomenon
involving both electrical and non-electrical process
parameters along with their complicated interrelationship.
REFERENCES
[1]. Nikhil Kumar and et al. (2012) ‘Comparative Study for
MRR on Die-sinking EDM using electrode of Copper and
Graphite’, International Journal of Advanced Technology
& Engineering Research (IJATER) Vol. 2, No. 2, 2012,
pp.170-174, ISSN NO: 2250-3536
[2]. Rajesh Choudhary and et al. (2010) 'Analysis and
evaluation of heat affected zones in electric discharge
machining of EN-3 I die steel', Indian Journal of
Engineering & Materials Sciences, Vol. 17, April 2010,
pp. 91-98
[3]. H S Payal and et al. (2008) 'Analysis of electro discharge
machined surfaces of EN-3 I tool steel', Journal of
Scientific & Industrial Research , Vol.67, December
2008, pp. 1072-1077
[4]. S.H.Tomadi and et al. (2009) ‘Analysis of the Influence of
EDM Parameters on Surface Quality, Material Removal
Rate and Electrode Wear of Tungsten Carbide’,
Proceedings of the International Multi-Conference of
Engineers and Computer Scientists 2009 Vol. II, IMECS
2009, March 2009, Hong Kong
[5]. J. A. Sa´nchez and et al. (2012) ‘Development of Optimum
Electrodischarge Machining Technology for Advanced
Ceramics’, International Journal of Advanced
Manufacturing Technology (2001) 18:897–905
[6]. Kuldeep Ojha and et al. (2010) ‘MRR Improvement in
Sinking Electrical Discharge Machining: A Review’,
Journal of Minerals & Materials Characterization &
Engineering, Vol. 9, No.8, pp.709-739, 2010
[7]. Hitesh B. Prajapati et al. (2013) ‘Parametric Analysis of
Material removal rate and surface roughness of Electro
Discharge Machining on EN 9’, International Journal of
Research in Modern Engineering and Emerging
Technology Vol. 1, Issue:1, 2013 ISSN:2320-6586
[8]. Sharanjit Singh and Arvind Bhardwaj (2011) ‘Review to
EDM by Using Water and Powder-Mixed Dielectric
Fluid’, Journal of Minerals & Materials Characterization
& Engineering, Vol. 10, No.2, pp.199-230, 2011

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Material Removal Rate, Tool Wear Rate and Surface Roughness Analysis of EDM Process